Some railroads have started removing these signs, which creates a hazard for operating crews and the public, according to the petition.

"Just as it is unreasonable for a motorist to know each speed restriction without a warning, the same is true for railroad crews," the unions wrote in the petition. "Unlike automobile travel, where speeds can be reduced promptly, trains are unable to comply with a speed restriction without prior knowledge."

The unions also asked for the standardization of the signs' dimensions, conspicuousness and color.